normal demo: work with odd number of columns :/

include/notcurses/notcurses.h

@@ -1157,7 +1157,9 @@ API struct ncplane* ncplane_below(struct ncplane* n);
 // Rotate the plane π/2 radians clockwise or counterclockwise. This cannot
 // be performed on arbitrary planes, because glyphs cannot be arbitrarily
 // rotated. The glyphs which can be rotated are limited: line-drawing
-// characters, spaces, half blocks, and full blocks.
+// characters, spaces, half blocks, and full blocks. The plane must have
+// an even number of columns. Use the ncvisual rotation for a more
+// flexible approach.
 API int ncplane_rotate_cw(struct ncplane* n);
 API int ncplane_rotate_ccw(struct ncplane* n);
 

src/demo/normal.c

@@ -81,6 +81,13 @@ int normal_demo(struct notcurses* nc){
   if(n == NULL){
     return -1;
   }
+  // we can't rotate a plane unless it has an even number of columns :/
+  int nx;
+  if((nx = ncplane_dim_x(n)) % 2){
+    if(ncplane_resize_simple(n, ncplane_dim_y(n), --nx)){
+      goto err;
+    }
+  }
   ncplane_erase(nstd);
   cell c = CELL_SIMPLE_INITIALIZER(' ');
   cell_set_fg_rgb(&c, 0xff, 0xff, 0xff);

src/lib/fill.c

@@ -519,6 +519,22 @@ rotate_merge(ncplane* n, ncplane* newp){
   return ret;
 }
 
+// generate a temporary plane that can hold the contents of n, rotated 90°
+static ncplane*
+rotate_plane(const ncplane* n){
+  int absy, absx;
+  ncplane_yx(n, &absy, &absx);
+  int dimy, dimx;
+  ncplane_dim_yx(n, &dimy, &dimx);
+  if(dimx % 2 != 0){
+    return NULL;
+  }
+  const int newy = dimx / 2;
+  const int newx = dimy * 2;
+  ncplane* newp = ncplane_new(n->nc, newy, newx, absy, absx, n->userptr);
+  return newp;
+}
+
 int ncplane_rotate_cw(ncplane* n){
   ncplane* newp = rotate_plane(n);
   if(newp == NULL){

src/lib/internal.h

@@ -638,9 +638,6 @@ memdup(const void* src, size_t len){
   return ret;
 }
 
-// generate a temporary plane that can hold the contents of n, rotated 90°
-ncplane* rotate_plane(const ncplane* n);
-
 void* bgra_to_rgba(const void* data, int rows, int rowstride, int cols);
 
 // find the "center" cell of two lengths. in the case of even rows/columns, we

src/lib/notcurses.c

@@ -2013,21 +2013,6 @@ int notcurses_inputready_fd(notcurses* n){
   return fileno(n->ttyinfp);
 }
 
-// generate a temporary plane that can hold the contents of n, rotated 90°
-ncplane* rotate_plane(const ncplane* n){
-  int absy, absx;
-  ncplane_yx(n, &absy, &absx);
-  int dimy, dimx;
-  ncplane_dim_yx(n, &dimy, &dimx);
-  if(dimx % 2 != 0){
-    return NULL;
-  }
-  const int newy = dimx / 2;
-  const int newx = dimy * 2;
-  ncplane* newp = ncplane_new(n->nc, newy, newx, absy, absx, n->userptr);
-  return newp;
-}
-
 uint32_t* ncplane_rgba(const ncplane* nc, int begy, int begx, int leny, int lenx){
   if(begy < 0 || begx < 0){
     return NULL;